1. Field of the Invention
The present invention relates generally to construction of stairways, and is directed more particularly to the use of prefabricated treadriser stair step units in combination with unnotched stringers.
2. Description of the Prior Art
In the past, stairways have generally been constructed using two or more parallel notched stringers extending between an upper floor and a lower floor of a building, with tread and riser members attached to and extending between corresponding notches of the stringers to form stair steps. The notches in each stringer are cut at right angles to facilitate the attachment of tread and riser members. As a result of the notching of the stringers, the physical strength of a given piece of lumber used for a stringer is reduced considerably. Consequently, the lumber used to make notched stringers must be considerably larger than would be required if the stringers were unnotched. This has resulted in increased cost of stairway construction over what would be encountered if solid stringers could be used. Furthermore, because of the varying floor space available for given stairways and the varying vertical distance between the lower and upper levels of buildings, notched stringers could not be mass-produced but had to be custom-made and, as a result, continued to be expensive. Thus the cost of building a stairway has remained inordinately high. Further practical problems have been encountered in some cases because of inaccurate calculations resulting in a bottom riser of a different vertical dimension than that of the remaining risers, and in other cases because of inaccurate notching of one stringer in a pair. If the notches on a given pair of stringers are not precisely matched, the tread and riser members align improperly, which results in a weakening of the stairway system and a shoddy-looking appearance. More recently, tread and riser members have been cut and prefabricated to fit upon unnotched stringers. However, such prefabricated stair step units have required toe cleats or other relatively expensive structural support in order to achieve the desired strength and proper attachment to the stringer. This has resulted in a stairway which is generally as expensive as, and sometimes more expensive than, the conventional stairway built with notched stringers. Applicant is unaware of any prior art which teaches the unique construction of the present invention.